Field of the Invention
This invention relates to water-soluble microcapsules. More particularly, this invention relates to water-soluble microcapsules which are stably retained in a concentrated aqueous solution containing an agent such as a surfactant and are readily dissolved in water or a dilute aqueous solution.
Numerous proposals have been made to date concerning the microcapsulation of enzymes. One of the methods so far proposed effects the microcapsulation of an enzyme by dispersing the enzyme and swelling particles in a liquid binder and spray drying the resultant dispersion (Japanese Patent Publication SHO 46(1971)-42594). The microcapsules produced by this method provide necessary protection for the enzyme so long as they are in a dry state. In water, they are dissolved to release the enzyme into the water. Another method effects the microcapsulation of an enzyme by dissolving the enzyme and an inorganic salt in a water-soluble liquid binder and spray drying the resultant solution (Japanese Patent Publication SHO 50(1975)-22506). The microcapsules obtained by this method protect the enzyme while in a dry state and dissolve in water to release the enzyme. A granular enzyme preparation proposed for use in a detergent is provided with a coating layer made of modified cellulose which is insoluble in water while in a neutral or acidic state and soluble in water while in an alkaline state (Japanese Patent Publication SHO 61(1986)-44471). All these conventional products are intended to contain an enzyme stably in a dry state therein and to be incorporated in a detergent similarly in a dry state. None of these prior techniques contemplates incorporating an enzyme in systems such as liquid detergent which contain water.
Inventions directed to effecting incorporation of detergent aids other than enzymes as contained in microcapsules have also been disclosed.
For example, a composition taught by one of these inventions is obtained by a process which comprises coating a cationic agent as with dextrin thereby forming microcapsules sensitive to water and incorporating the microcapsules in an anhydrous anionic shampoo (Japanese Patent Public Disclosure SHO 50(1975)-3105). In this case, since the microcapsules by nature release their contents on contact with water, the shampoo intended to incorporate these microcapsules is required to be in an anhydrous state. Microcapsules which are coated with a special copolymer insoluble in an alkaline water and soluble in a neutral or acidic water are also disclosed (Japanese Patent Public Disclosure SHO 61(1986)-28440 and SHO 61(1986)-28441. In the specifications of these inventions, it is stated that when the microcapsules are produced by using a fabric softener or other similar laundry aid as a core material, they can be used for incorporation in detergents. In this case, the microcapsules are intended to permit the fabric softener contained therein to be released therefrom in consequence of changes of the pH value of the laundering liquid at the stages of washing, dehydrating, and rinsing during the course of laundering. Many of the conventional enzyme-containing microcapsules are adapted to encapsulate various enzymes with semipermeable membranes for the purpose of immobilizing the enzymes (Japanese Patent Public Disclosure SHO 52(1977)-3890, SHO 55(1980)-44387, SHO 60(1985)-110330 and SHO 60(1985)-75326). These microcapsules are all insoluble in water.
Many proposals have been made in the field of medical preparations, such as intestinally soluble microcapsules (Japanese Patent Public Disclosure SHO 58(1983)-55413 and SHO 58(1983)-67616) and microcapsules adapted for gradual release of their contents (Japanese Patent Public Disclosure SHO 58(1983)-53110 and SHO 60(1985)-100516).